Celecoxib. Computer molecular model of celecoxib (molecular formula: C17.H14.F3.O2.S), a non- steroidal anti-inflammatory drug (NSAID). It is composed of carbon (grey), hydrogen (white), oxygen (red), sulphur (yellow), nitrogen (blue) and fluorine (green). Celecoxib works by inhibiting the COX-2 form of the cyclo-oxygenase enzyme, which in turn inhibits the production of prostaglandins.